U.S. patent number 10,632,538 [Application Number 15/317,660] was granted by the patent office on 2020-04-28 for method and press for producing a green compact composite with a predetermined breaking point.
This patent grant is currently assigned to GKN Sinter Metals Engineering GmbH. The grantee listed for this patent is GKN Sinter Metals Engineering GmbH. Invention is credited to Eberhard Ernst, Alexander Hullen, Rainer Schmitt.
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United States Patent |
10,632,538 |
Hullen , et al. |
April 28, 2020 |
Method and press for producing a green compact composite with a
predetermined breaking point
Abstract
The invention relates to a method for producing a green compact
composite comprising at least a first partial green compact and a
second partial green compact, wherein, within one pressing cycle, a
powder is introduced into a filling chamber and then separated into
a first partial quantity and into a second partial quantity, and,
within the same pressing cycle, the respective partial quantities
are pressed to form a first partial green compact and a second
partial green compact and the partial green compacts are
amalgamated after the pressing, wherein the amalgamation forms a
press fit between the first partial green compact and the second
partial green compact and produces a predetermined breaking point
in the green compact composite. Furthermore, the invention proposes
a green compact composite, a sintered component and also a press,
each of which can be based on the proposed method.
Inventors: |
Hullen; Alexander (Wachtberg,
DE), Schmitt; Rainer (Wachtberg, DE),
Ernst; Eberhard (Eichenzell, DE) |
Applicant: |
Name |
City |
State |
Country |
Type |
GKN Sinter Metals Engineering GmbH |
Radevormwald |
N/A |
DE |
|
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Assignee: |
GKN Sinter Metals Engineering
GmbH (Radevormwald, DE)
|
Family
ID: |
53434318 |
Appl.
No.: |
15/317,660 |
Filed: |
June 10, 2015 |
PCT
Filed: |
June 10, 2015 |
PCT No.: |
PCT/EP2015/062991 |
371(c)(1),(2),(4) Date: |
December 09, 2016 |
PCT
Pub. No.: |
WO2015/189300 |
PCT
Pub. Date: |
December 17, 2015 |
Prior Publication Data
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|
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Document
Identifier |
Publication Date |
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US 20170113276 A1 |
Apr 27, 2017 |
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Foreign Application Priority Data
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|
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Jun 10, 2014 [DE] |
|
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10 2014 008 169 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B22F
3/11 (20130101); B22F 3/16 (20130101); B22F
3/04 (20130101); B22F 3/03 (20130101); F16D
9/06 (20130101); F16D 1/0858 (20130101); B22F
5/10 (20130101); B22F 5/003 (20130101); B30B
11/005 (20130101); B22F 7/06 (20130101); B30B
11/027 (20130101); B22F 7/062 (20130101); F16D
9/08 (20130101); B22F 2003/033 (20130101); F16D
2001/102 (20130101); B22F 2207/17 (20130101); B22F
2998/10 (20130101); F16D 1/10 (20130101) |
Current International
Class: |
B22F
7/06 (20060101); B22F 5/00 (20060101); B22F
3/03 (20060101); B30B 11/00 (20060101); B22F
3/16 (20060101); B22F 3/04 (20060101); F16D
1/08 (20060101); F16D 9/08 (20060101); F16D
9/06 (20060101); B22F 5/10 (20060101); B22F
3/11 (20060101); B30B 11/02 (20060101); F16D
1/10 (20060101) |
Field of
Search: |
;419/38 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
|
|
|
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10 2009 016718 |
|
Oct 2010 |
|
DE |
|
10 2009 042598 |
|
Mar 2011 |
|
DE |
|
0 399 630 |
|
Nov 1990 |
|
EP |
|
8134509 |
|
May 1996 |
|
JP |
|
WO-2010115502 |
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Oct 2010 |
|
WO |
|
Other References
PCT International Search Report for corresponding International
Application No. PCT/EP2015/062991; dated Oct. 1, 2015. cited by
applicant.
|
Primary Examiner: Zhu; Weiping
Attorney, Agent or Firm: Quarles & Brady LLP
Claims
The invention claimed is:
1. A method for producing a green product composite, having at
least a first partial green product and a second partial green
product, in a press, wherein, within a pressing cycle, a powder is
introduced into a filling chamber of the press and is subsequently
separated into a first partial amount and a second partial amount
in the press, within the same pressing cycle, the respective
partial amounts are pressed to form a first partial green product
and a second partial green product, with homogeneous compaction in
each case, and the partial green products are, after the pressing
in the press, joined to form the green product composite, wherein,
by way of the joining, an interference fit is formed between the
first partial green product and the second partial green product,
and at least one predetermined breaking point is formed in the
green product composite.
2. The method as claimed in claim 1, wherein the green product
composite is sintered to form a unit, and a predetermined breaking
point of the unit is formed in a region in the vicinity of the
interference fit.
3. The method as claimed in claim 2, wherein, after the
amalgamation of the first partial green product with the second
partial green product to form the green product composite, the
latter is sintered to form the unit without joint re-compaction of
the first and of the second partial green product in the green
product composite.
4. The method as claimed in claim 1, wherein the green product
composite and/or the sintered unit is formed by virtue of said
green product composite or said sintered unit having a first
component composed of the first partial green product with a first
density and having a second component composed of the second
partial green product with a second density which is greater than
the first density, wherein the predetermined breaking point of the
green product composite and/or of the sintered unit is formed in
the first component with the first, relatively low density.
5. The method as claimed in claim 1, wherein the first and the
second partial green product are compacted in each case
homogeneously and with the same or different density.
6. The method as claimed in claim 1, wherein a different density is
achieved in the pressing of the first partial green product than in
the pressing of the second partial green product.
7. The method as claimed in claim 1, wherein the at least one
predetermined breaking point is outside the interference fit.
8. The method of claimed in claim 1, wherein the at least one
predetermined breaking point is a notching.
9. A method for configuring a sintered unit or green product
composite with a predefined failure load for a predetermined break,
in particular a predetermined breaking point, having the following
steps: producing a first sintered unit or a first green product
composite as claimed in claim 1; subjecting the first unit and/or
the green product composite to load until the point of failure of
the unit and/or of the green product composite; detecting a failure
load; detecting a deviation of the detected failure load from the
predefined failure load; varying a predefined pressing pressure
during an execution of the method as claimed in claim 1, in order
to achieve a different density in the pressing of the first or
second partial green product, in the event of the deviation
exceeding a predefined tolerance value; repeating one or more of
the preceding steps until the deviation undershoots the tolerance
value.
Description
This application represents the U.S. national stage entry of PCT
International Application No. PCT/EP2015/062991 filed Jun. 10,
2015, which claims priority to German Patent Application No. 10
2014 008 169.9 filed Jun. 10, 2014, the disclosures of which are
incorporated herein by reference in their entirety and for all
purposes.
The invention relates to a method and a press for producing a green
product composite having at least a first partial green product and
a second partial green product, wherein, within a pressing cycle in
the press, a powder is introduced into a filling chamber and is
subsequently separated into a first partial amount and a second
partial amount, and within the same pressing cycle, the respective
partial amounts are pressed in each case homogeneously to form a
first partial green product and a second partial green product, and
the partial green products are, after the pressing in the press,
amalgamated.
EP-B-0 399 630 has disclosed a method for producing a green product
composite, wherein a powder material is pre-compacted to form a
first green product and, subsequently, a second, separately
pre-compacted green product or a solid part is inserted into the
press into a cavity of the first green product. Thereafter, the
assembled green product is compacted. Green products manufactured
in this way, and sintered units produced therefrom, are, both
during the compaction itself and during the demolding process and
during subsequent handling, at risk of cracking at cross-sectional
transitions inter alia owing to density inhomogeneities or axial
and radial stresses in the tool.
By way of a method proposed in DE-A-10 2009 042 598, it is sought
to avoid the risk of cracking during the pressing process at the
transitions of different cross sections of the green product, which
arises for example owing to stresses in the tool or uncontrolled
powder flow from one cross section into an adjacent cross section.
In the case of said method, at least two partial green products are
compacted independently of one another, without disruptive
influences at cross-sectional change transitions, and are
subsequently joined, wherein the compaction of the two partial
green products and the subsequent joining are performed in a press
tool within a pressing cycle. By way of said method, green product
composites and sintered units are produced which have a homogeneous
density over the entire green product composite or the sintered
unit.
JP-A-08134509 describes a further method for producing a composite
of green products composed of different materials. DE-A-10 2009 016
718 describes a sintered unit with a predetermined breaking point
which is realized, in terms of construction, by way of selective
thickness reduction of the unit. Pressing and sintering of two or
more green products does not take place.
During production of a sintered unit which is sintered from at
least two partial green products in the green product composite,
said known method has the advantage that the unit, owing to the
homogeneous density throughout the sintered unit, has no
significant, and in particular no predictable, structural weak
points owing to density inhomogeneities or prior damage resulting
from cracks.
It is an object of the present invention to provide a green product
composite which exhibits predictable behavior and which makes it
possible here to realize an advantage from the assembly of the
green product composite from partial green products, wherein the
manufacturing advantage of the use of a single press is
maintained.
Advantages features, embodiments and refinements emerge from the
following description, from the figures and from the claims,
wherein individual features from one embodiment are not restricted
thereto. Rather, one or more features from one embodiment may be
combined with one or more features from another embodiment to form
further embodiments. Also, the wordings of the independent claims
in their form as filed should not be understood to constitute a
limitation of the subjects to be claimed. One or more features of
the wordings may therefore be exchanged and omitted, but likewise
additionally supplemented. Also, the features specified on the
basis of a specific exemplary embodiment may also likewise be used
in generalized form and/or in other exemplary embodiments, in
particular uses.
A method for producing a green product composite, having at least a
first partial green product and a second partial green product, in
a press is proposed, wherein, within a pressing cycle, a powder is
introduced into a filling chamber of the press and is subsequently
separated into a first partial amount and a second partial amount
in the press, and within the same pressing cycle, the respective
partial amounts are pressed to form a first partial green product
and a second partial green product. It is preferably the case that
a different density is achieved in the pressing of the first
partial green product than in the pressing of the second partial
green product. The partial green products are, after the pressing
in the press, amalgamated to form the green product composite,
wherein, by way of the amalgamation, an interference fit is formed
between the first partial green product and the second partial
green product. A predetermined breaking point of the green product
composite is formed preferably in a region in the vicinity of the
interference fit, preferably outside the interference fit. By way
of the joining of the first partial green product to the second
partial green product, an interference fit is formed between the
first partial green product and the second partial green product.
For this purpose, it is provided for example that at least one of
the two partial green products has an oversize. It is preferable if
only one of the two partial green products has an oversize. A
further embodiment provides that the two partial green products may
each have an oversize. The respective dimensions of upper and lower
plunger are preferably such that, during a respective pressing
process of the partial green products, a pressure is built up which
the partial green products cannot laterally evade owing to the
lateral delimitation by abutting parts of the pressing tool; it
rather being the case as a result that, aside from an axial
pressure exerted by upper and lower plunger, a radial pressure is
also generated which can be utilized to generate the interference
fit by joining of the two partial green products. For example, a
predetermined breaking point of the green product composite is
formed in a region adjacent to the interference fit.
The proposed method provides that the filling of the filling
chamber with the powder, the subsequent separation of the powder
into the first and the second partial amount, the pressing of the
first and second partial green product, the joining of the first
partial green product to the second partial green product to form
the green product composite and the subsequent removal of the green
product composite take place within a pressing cycle. The
production of the green product composite is performed by way of a
single press which has at least a first lower plunger, a first
upper plunger, a second lower plunger and a second upper plunger.
The production of the green product composite is particularly
preferably performed by way of a single pressing tool. The proposed
method provides for the first and the second partial amounts to
have the same constituents, that is to say in particular the same
powder to be sintered, for example the same powder mixture or
powder alloy, wherein the two partial amounts preferably have
entirely different densities.
In the case of the invention, at least two partial green products
composed of the same powder material and with possibly entirely
different densities are pressed in each case homogeneously within a
tool, wherein the partial green products are then joined one inside
the other under pressure. The joining is subsequently sintered
(possibly with a slightly lower strength than the base material).
The aim here is for example to set the density of a partial green
product such that that component of the unit which corresponds to
said partial green product after the sintering fails, at the
transition to another component which corresponds to the other
partial green product and into which the first component is joined,
under the action of the structurally predefined notch effect under
predictable conditions. According to the invention, it is not the
case that the failure takes place at the joining surface of two
components; it is rather the case that the weaker component fails,
which is normally the plugged-in component, for example by way of a
shearing-off action. According to the invention, it is thus the
case after the sintering that no further processing steps for
notching or the like are required in order to produce the
predetermined breaking point.
According to the invention, it is thus the case, by way of the
assembly of the two in each case homogeneously pressed partial
green products and the coordination thereof with one another, that
a predefinable, defined predetermined break, that is to say a
predetermined breaking point, is provided. This is achieved by
virtue of in each case two partial green products to be joined to
one another being in each case homogeneously compacted. In this
way, random material weakenings, such as extremely small cracks or
the like, in the partial green products are avoided. Normally, said
"material weakenings" are the cause of failure of the later
sintered unit. By way of tests, it has been found that one partial
green product may be designed so as to be held in a later fully
sintered unit securely up to a predefinable force or up to a
predefinable torque, and so as to fail only when said force or said
torque is exceeded. By way of the homogeneous compaction in the
case of the "green-in-green" production according to the invention,
it is thus possible to actually predefine a load limit and thus a
predetermined breaking point, the precise position of which is
possibly not exactly predictable. However, there are no longer
deviations with regard to the failure owing to defects in the
material or the like or at interfaces, such as was the case in
previous assembled partial green products not homogeneously
compacted according to the invention. In particular, the risk of
crack at a transition point, such as is possible owing to
inhomogeneities in the case of normal, conventional manufacture
according to the prior art, is prevented. A transition point is in
this case to be understood for example to mean the transition, in
particular gusset, from a first to a second dimension, in
particular from a first to a second diameter, which, with the use
of conventional technology for the production of green products,
exhibits unpredictable breaks and therefore does not make it
possible to reliably permit a predictable predetermined break in
the case of sintered units with transitions.
According to the invention, it is furthermore also possible for a
unit to be equipped with different predetermined breaks and thus
with different predetermined breaking points. It is thus possible
for different partial green products with different failure
strengths to be joined one inside the other by way of the
"green-in-green" production according to the invention. This leads
to a sintered unit in which, for example, a first component
exhibits a predetermined break when a first load threshold is
exceeded, whereas a second component experiences a predetermined
break only when a second load threshold, which is higher than the
first load threshold, is exceeded. In other words, it is thus
possible for a unit produced according to the invention to exhibit
at least two predefinable, mutually different predetermined breaks.
In general, it is the case here that a unit of said type is then
also produced by sintering of a green product composite composed of
more than two partial green products.
A refinement provides that the sintered unit has a first and a
second predefinable predetermined break which can be triggered at
mutually different loads, wherein the first and the second
predetermined break are situated in respectively different regions
of the sintered unit. This is realized for example by way of a
green product composite in which partial green products are joined
concentrically with respect to one another and/or are arranged and
joined adjacent to one another in a partial green product.
Below, upper and lower plunger are also referred to as pressing
plungers. Upper and lower plunger are part of the pressing tool. In
particular, it is possible by way of a pressing tool, in particular
a pressing plunger, for powder material to be pressed, that is to
say compacted, wherein joining of partial green products is also
performed by way of the same pressing tool. In a further embodiment
of the proposed method, it is provided that, during a separation of
the powder into the first and the second partial amount by way of
the pressing tool of a pressing plunger, a joining chamber is kept
free by way of a pressing plunger. In particular, said joining
chamber is at least partially delimited by the first or second
partial amount of the powder substance. A joining chamber is to be
understood to mean the chamber within a partial amount or a partial
green product, into which chamber a further partial green product
is joined.
It is particularly advantageous for the partial green products to
be pressed in the same tool. In particular, it is possible for at
least one partial green product to be pre-compacted and to be
re-compacted or finally compacted before or after the joining of
the two partial green products to form the green product composite.
In a further embodiment, it is provided that the joint green
product composite is re-compacted or finally compacted preferably
in the same tool. It is particularly advantageously provided that,
after the joining of the first partial green product to the second
partial green product, the two partial green products are sintered
to form the unit without joint re-compaction. Furthermore, aside
from the first and second partial green product, at least one
further partial green product, for example a third, a fourth or a
fifth partial green product, may be pressed and joined within a
pressing cycle to form a green product composite.
The pressing plungers are movable relative to one another such that
at least the first and second lower and upper plungers can, in a
first state of the press, form the filling chamber for the (common
or identical) powder for the pressing of the first and of the
second partial green product. The first and second lower and upper
plungers are preferably, in a second state of the press, arranged
relative to one another such that the common powder is present in
the form of a first partial amount and in the form of a second
partial amount, wherein the first partial amount is separated from
the second partial amount.
In a third state of the press, the first and second lower and upper
plungers are arranged relative to one another such that a pressed
first partial green product is present between the first lower
plunger and the first upper plunger and a pressed second partial
green product is present between the second lower plunger and the
second upper plunger. The pressing is preferably performed such
that the first and also the second partial green product are in
each case homogeneously compacted. In this context, homogeneously
means that as far as possible no density deviation exists within
the respective partial green product. Rather, each partial green
product has in each case an at least approximately equal density as
viewed over the cross section thereof. The density of the first
partial green product preferably differs from the density of the
second partial green product. In a fourth state of the press, the
first partial green product is pressed with the second green
product to form a green product composite, wherein an interference
fit is formed between the first partial green product and the
second partial green product. The interference fit may preferably
be varied by way of a plunger clearance between two pressing
plungers.
In the proposed method, a time offset may be provided between the
third state and the fourth state. In a modification thereof, the
joining of the first partial green product to the second partial
green product takes place still during the pressing of the first
and/or of the second partial green product. At the start of the
pressing of the first and/or of the second partial green product,
the first partial amount is present separately from the second
partial amount, which means that no powder particles of the first
partial amount come into contact with other powder particles of the
second partial amount.
The separation of the powder into the first and the second partial
amount is preferably realized by way of a movement of at least one
pressing plunger, of the first and/or second lower plunger and/or
upper plunger. In particular, for this purpose, use may be made of
a method, and also in principle a press setup, as disclosed in
DE-A-10 2009 042 598. The content of said document is incorporated
by reference into the subject matter of the present patent
application.
In particular, after the separation of the powder into two partial
amounts, the pressing plungers form a first working chamber and a
second working chamber. A working chamber is to be understood in
particular to mean cavities in a pressing tool which can be filled
with powder and in which a pressing process or a compaction of the
powder can be performed. The working chambers are preferably
delimited at least by one pressing plunger. In a refinement, one of
the working chambers is delimited by at least two pressing plungers
and/or by a die. The first and/or the second working chamber are/is
particularly preferably movable within the pressing tool, and
preferably, at least one of the working chambers, the first and/or
the second working chamber, is moved during the pressing of the
first and/or second partial green product.
As proposed, by way of the joining of the first partial green
product to the second partial green product, an interference fit is
formed between the first partial green product and the second
partial green product, wherein a predetermined breaking point of
the green product composite is preferably formed in the region of
the vicinity of the interference fit. The interference fit between
the first and the second partial green product effects mechanical
clamping of the partial green products, which holds the green
product composite together, which is sufficient for the transfer of
the green product composite to the sintering furnace. The partial
green products preferably have, in at least a subregion of the
contact surfaces, a contact pressure of between 0.1 N/mm.sup.2 and
100 N/mm.sup.2, more preferably between 1 N/mm.sup.2 and 50
N/mm.sup.2, and particularly preferably between 2 N/mm.sup.2 and 30
N/mm.sup.2. The interference fit preferably promotes the sintering
of the green product composite, wherein, by way of the interference
fit, diffusion processes during the sintering are promoted in
relation to a green product composite without an interference fit,
for example with cavities between the individual partial green
products.
In particular, the interference fit may be effected by way of a
plunger clearance between the first lower or upper plunger and the
second lower or upper plunger. Here, it is provided that, at least
by way of a second lower or upper plunger, a joining chamber is
kept free in which the second partial green product is displaced
for the purposes of joining to the first partial green product. The
pressing plunger which keeps a joining chamber free has, in
particular, a slightly smaller diameter than the second partial
green product which is joined into the joining chamber. The
difference or the oversize corresponds to the plunger clearance
between the first lower or upper plunger and the second lower or
upper plunger. In one embodiment, the plunger clearance lies
between approximately 0.005 mm and approximately 0.025 mm, and in a
further embodiment, it lies between approximately 0.025 mm and
approximately 0.05 mm.
After the joining of the first partial green product to the second
partial green product, the predetermined breaking point of the
green product composite is present in a region in the vicinity of
the interference fit.
The interference fit may in particular be situated in a plane which
extends perpendicular to the joining direction, wherein the joining
direction is predefined by a relative movement of the first partial
green product relative to the second partial green product during
the joining to form the green product composite. In said plane, the
interference fit has a width and a length oriented perpendicular to
the width. The region in which the predetermined breaking point of
the green product composite is arranged may preferably be
predefined by way of the proposed method. In an embodiment, the
region extends from the interference fit in a direction away from
the interference fit and parallel to the joining direction as far
as a distance which amounts to one tenth of the value of the square
root of the product of the length and of the width of the
interference fit. In a further embodiment, said spacing amounts to
one fifth of the value of said square root, and in a modified
embodiment in relation thereto, the spacing amounts to one third of
the value of said square root.
In an advantageous embodiment of the method, an interference fit is
generated which is formed firstly parallel to the joining direction
and secondly for example in circular form, or in the form of a
hexagon, in a plane perpendicular to the joining direction.
It is furthermore provided that, during the pressing of the first
partial green product and during the pressing of the second partial
green product, two partial green products with a different density
are formed. In a further embodiment of the method, the green
product composite is sintered to form a unit, wherein a
predetermined breaking point of the unit is formed preferably in a
region in the vicinity of the interference fit of the green product
composite.
The predetermined breaking point of the green product composite is
particularly advantageously arranged at the same location as the
predetermined breaking point of the sintered unit. Here, the
predetermined breaking point of the green product composite however
fails at a considerably lower failure load than the predetermined
breaking point of the sintered unit.
It is particularly advantageously provided that the green product
composite and/or the sintered unit has a first component composed
of the first partial green product with a first density and a
second component composed of the second partial green product with
a second density which is greater than the first density. The
predetermined breaking point of the green product composite and/or
of the sintered unit is preferably arranged in the first component
with the first, relatively low density.
In an embodiment, a density difference between the first and the
second partial green product in the green product composite amounts
to at least 0.1 g/cm.sup.3 or greater. A deviation of a respective
homogeneous density between first and second partial green product
preferably lies between 0.1 g/cm.sup.3 and 1.3 g/cm.sup.3. In the
case of a sintered unit, it is the case in an embodiment that the
density difference between the first and the second component
amounts to at least 0.1 g/cm.sup.3, preferably at least 0.5
g/cm.sup.3. An embodiment provides, in the case of a sintered unit
having a first and a second component composed of the first and the
second partial green product respectively, that the density
difference lies between 0.1 g/cm.sup.3 and 1.1 g/cm.sup.3. For
example, the first component may have a density in a range between
6.8 and 7.4 g/cm.sup.3, and the second component may have a density
between 6.2 and 7.0 g/cm.sup.3.
The first density and the second density can in particular be
categorized into individual SINT classes, in particular different
SINT classes. Materials for sintered molded parts are, in terms of
their characteristics and designations, standardized in material
performance specifications conforming to DIN 30910. Here, for the
categorization of the materials, different density classes, that is
to say SINT classes, are used. The density classes comprise inter
alia the density classes A, B, C, D and E, wherein A denotes the
density class with the lowest density and E denotes the density
class with the highest density, and the classes A, B, C, D and E
have increasing densities in the stated sequence.
It is particularly advantageously possible for a failure load of
the sintered unit and/or of the green product composite at which
the sintered unit and/or the green product composite fails at the
predetermined breaking point to be achieved by way of a
reproducible density difference between the first and the second
density. In a preferred embodiment, the difference amounts to one
SINT class, that is to say the first density may for example be
assigned to the density class A and the second density may be
assigned to the density class B, or the first density may be
assigned to the density class C and the second density may be
assigned to the density class D. In a further embodiment, the
density difference has two SINT classes, that is to say the first
density may for example be assigned to the density class A and the
second density may be assigned to the density class C, or the first
density may be assigned to the density class C and the second
density may be assigned to the density class E. Correspondingly,
density differences of up to three, four or five SINT classes are
also possible.
Furthermore, the partial green product or the component with the
relatively low density and the predetermined breaking point may be
arranged in the interior of the green product composite and/or
sintered unit, whereas the exterior of the green product composite
and/or of the sintered unit has a relatively high density,
preferably without a predetermined breaking point. A further
embodiment provides, by contrast, that the partial green product
and/or the component with the relatively low density and the
predetermined breaking point is arranged at the exterior of the
green product composite and/or sintered unit, whereas a relatively
high density, preferably without a predetermined breaking point, is
present in the interior of the green product composite and/or of
the sintered unit. Depending on the green product composite and/or
sintered unit, it is also possible for some other geometrical
arrangement, also a varying arrangement along an extent of the unit
and/or of the green product composite, to be provided. As an
alternative to a single predetermined breaking point, it is also
possible for two or more predetermined breaking points to be
provided. For example, in each case at least one predetermined
breaking point may be provided in different planes and/or at
different extents of a sintered unit and/or of a green product
composite. This may be advantageous for example in the case of a
unit which is subjected to different forces and moments from
different directions.
The density difference between the first and the second partial
green product is preferably set by way of a control unit which
controls the positions of the pressing plungers during the
introduction of the powder into the filling chamber and during the
separation of the powder into the first and second partial amounts.
The density difference may preferably be converted, by way of the
density of the pore-free powder before the pressing, into a direct
SINT class difference. Such a conversion is however reliably
possible only if the two partial green products have a very
homogeneous density distribution, in particular if the first
partial green product is pressed separately from the second partial
green product, and preferably both partial green products are
pressed and joined within the same pressing cycle.
The failure load at the predetermined breaking point is preferably
specified as a failure tensile stress, failure shear stress and/or
failure pressure. Furthermore, the failure load may also be
specified as an equivalent stress, in particular as a von Mises
equivalent stress.
It is particularly preferably the case in the proposed method that,
two partial green products with a predefined density difference are
produced in a manner dependent on the failure load at the
predetermined breaking point at which the sintered unit or the
green product composite fails at the predetermined breaking
point.
For example, it is possible, in the case of a von Mises equivalent
stress of approximately 300 N/mm.sup.2, for a density difference of
one SINT class to be selected, that is to say the first density is
for example assigned to the SINT class B and the second density is
assigned to the SINT class C. In a further embodiment, in the case
of, for example, a von Mises equivalent stress of approximately 500
N/mm.sup.2, the first density may be assigned to the SINT class C
and the second density may be assigned to the SINT class D, and in
a further exemplary embodiment, in the case of a von Mises
equivalent stress of approximately 600 N/mm.sup.2, the first
density may be assigned to the SINT class E and the second density
may be assigned to the SINT class F, which preferably has tempered
metal powder alloys. To realize a tempered sintered unit, it is for
example possible for bromine, manganese, vanadium, tungsten and/or
molybdenum to be introduced into the powder. Such precipitation
hardening is also possible in the case of the SINT classes A, B, C,
D and E. It is preferably also the case in this configuration that
the first partial green product and the second partial green
product have the same alloy, which is however compacted with
different levels of intensity.
Furthermore, a method for configuring a sintered unit or green
product composite with a predefined failure load for a
predetermined breaking point is proposed, wherein the green product
composite is produced by way of the proposed method. The method for
configuration comprises the following steps: in a first step, a
first unit or a first green product composite is produced. In a
second step, the unit and/or the green product composite is
subjected to load to the point of failure of the unit and/or of the
green product composite. In a third step, said failure load is
detected. The failure load is preferably detected in the form of a
tensile and/or shear stress and/or a pressure load. This may be
performed for example by way of at least one strain gauge on the
green product composite or the sintered unit. In a fourth step, a
deviation of the detected failure load from the predefined failure
load is detected. If the deviation exceeds a predefined tolerance
value, then in a fifth step, at least one parameter is varied in
order to achieve a different density for example of a first or
second partial green product of the green product composite during
the execution of the method according to the invention. For
example, a predefined force on a pressing plunger during the
pressing of the first or second partial green product may be
varied. One of the steps 1 to 5, particularly preferably all of the
steps 1 to 5, are repeated until the detected deviation reaches
and/or falls below the predefined tolerance value.
Said unit production method has the advantage over a casting method
in particular that the unit is defined with a predefined
predetermined breaking point, in particular with regard to location
and failure load at which the predetermined breaking point is
intended to be destroyed, not by way of the shaping of the unit
alone. Rather, by way of a variation which is performed during the
pressing process of the first or of the second partial green
product, a density difference between the first and the second
partial green product can be set, which density difference
corresponds to a predefined failure load for the predetermined
breaking point of the fully sintered unit. It is also possible in
this way for very lightweight units to be manufactured with the
same shape but differently dimensioned predetermined breaking
points, that is to say with predetermined breaking points with in
each case different predefined failure loads, without the need here
to change and/or exchange the tool of the press.
Furthermore, a green product composite is proposed which has a
first partial green product and a second partial green product,
wherein the first partial green product and the second partial
green product are connected by way of an interference fit. The
first and the second partial green product are composed in each
case of the same powder. The first and the second partial green
product are in each case homogeneously compacted and have different
densities, and a predetermined breaking point is provided in that
partial green product which has the relatively low density. A
predetermined breaking point is provided preferably in the vicinity
of the interference fit. It is furthermore preferable for the
proposed green product composite to be produced by way of a method
and/or a press as described in more detail above and/or below.
Furthermore, a sintered unit is proposed, having a first component
and a second component which are joined together and are sintered
to form the unit, wherein the first component has a density which
differs from the density of the second component, and wherein that
one of the two components which has a relatively low density has a
predetermined breaking point, and has said predetermined breaking
point in particular owing to the relatively low density. The
sintered unit is preferably produced as a green product composite
as described in more detail above and also below.
Furthermore, the use of a sintered unit is proposed, wherein the
unit is in the form of a structural element of a machine. The
structural element can be destroyed under the action of a
predefined failure load at the predetermined breaking point.
Furthermore, the sintered unit may be used as part of an adapter
which can be destroyed under the action of a predefined failure
load at the predetermined breaking point. The adapter may in
particular be suitable for the fixing of machine parts by screw
connection.
In an advantageous refinement, it is provided that the unit is in
the form of a structural element of a bodyshell, preferably of a
motor vehicle, and can be destroyed under the action of a one-off
load in the form, for example, of a tensile stress, compressive
stress and/or shear stress with a predefinable minimum value at the
predetermined breaking point (e.g. screws for the fastening of
shafts with a controlled torque). In particular, the unit may have
a safety function in the event of the motor vehicle being involved
in a collision. An example here is a unit for a steering wheel
locking means which must fail, that is to say yield, in a defined
manner in the event of a collision.
Furthermore, the unit may be in the form of a part of a tension
device, preferably of a cable pull device, and may be capable of
being destroyed under the action of a one-off tensile stress load
involving an exceedance of a predefinable value at the
predetermined breaking point.
A further use provides for the unit to be in the form of a
structural element of an engine block or of an energy accumulator
and to be capable of being destroyed under the action of a one-off
load with a predefinable value of a tensile stress, compressive
stress and/or shear stress at the predetermined breaking point. The
predetermined breaking point is advantageously oriented such that a
part of an engine block or energy accumulator slides under the
passenger compartment of the motor vehicle in the event of the
motor vehicle being involved in a collision. It is also possible
for the unit to be in the form of a structural element of a gearbox
shaft or of a drive shaft.
Also proposed is a press having a control unit and having a
pressing tool for producing a green product composite. The green
product composite comprises at least a first partial green product
and a second partial green product, wherein the first partial green
product is pressed together with the second partial green product.
The pressing tool has at least a die, a first upper plunger, a
first lower plunger, a second upper plunger and a second lower
plunger. The first and/or the second upper and lower plungers
respectively are movable relative to one another, wherein the first
and second upper and lower plungers, in a first state, form a
common filling chamber for a common powder for production of the
first and of the second partial green product. In a second state of
the first and second lower and upper plungers, the powder is
present separately in the form of a first partial amount and in the
form of a second partial amount. In a third state of the first and
second lower and upper plungers, a pressed first partial green
product is present between the first lower plunger and the first
upper plunger and a pressed second partial green product is present
between the second lower plunger and the second upper plunger,
wherein the control unit predefines a first pressing pressure
between the first upper plunger and the first partial amount and a
second pressing pressure between the second upper plunger and the
second partial amount, wherein the first partial green product and
the second partial green product are pressed with in each case
different density, and an amalgamation of the first partial green
product with the second partial green product to form a green
product composite is realized by way of movement of the plunger
pairs controlled by the control unit, wherein, after the
amalgamation, an interference fit is formed between the first
partial green product and the second partial green product, and a
predetermined breaking point of the green product composite is
formed in a region in the vicinity of the interference fit.
In an advantageous embodiment of the press, it is provided that the
first upper plunger and the second lower plunger are arranged
adjacent to one another along a line of action of a pressing force
of the first upper plunger, wherein the first upper plunger and the
second lower plunger have in each case a first pressing surface and
a second pressing surface which run parallel to one another and
which are oriented obliquely with respect to at least one pressing
surface of the first lower plunger and/or of the second upper
plunger. In a refinement, the first pressing surface of the first
upper plunger and the second pressing surface of the second lower
plunger may also be oriented perpendicular to at least one pressing
surface of the first lower plunger and/or of the second upper
plunger.
A further embodiment of the press provides for the control unit to
have a memory in which position regulation at least of a first or
second lower or upper plunger in relation to the pressing tool is
stored as a function of the magnitude of a predefined failure load
of a predetermined breaking point. For example, in a manner
dependent on a density of the first or second partial green product
to be achieved in the pressing process, a particular position of
the first or second lower or upper plunger shortly before the start
of the pressing process in relation to the pressing tool may be
stored. It is also possible for an absolute distance of the first
or second lower plunger from the first or second upper plunger
before the start of the pressing process of the first or second
partial green product to be stored. The position regulation
preferably comprises the relative position of the first or second
lower or upper plunger relative to the tool, or an absolute
distance of the first or second lower plunger from the first and/or
second upper plunger in each case before the start of the pressing
process of the first or second partial green product, as a setpoint
value during the movement of the pressing plunger before the start
of the pressing process.
It is furthermore also possible for a subsequent surface processing
and/or treatment to be provided, for example by way of coating or
the like. A surface is preferably motivated to undergo oxidization.
This makes it possible, for example, to realize a greater force
resistance along with increased brittleness. It is preferably the
case that at least that surface of that component which is intended
to predictably fail is for example subjected to pretreatment with
superheated steam.
Further advantageous embodiments and features will emerge from the
following figures and from the associated description. The
individual features which emerge from the figures and from the
description are merely exemplary and do not restrict the respective
embodiment. It is rather possible for one or more features from one
or more figures to be combined with other features from the above
description to form further embodiments. Therefore, the features
are specified not in a limiting manner but in an exemplary manner.
In detail:
FIG. 1 shows a perspective view of a sintered unit,
FIG. 2 shows a perspective view of a first partial green product
and a second partial green product,
FIG. 3 shows a sectional view of the sintered unit from FIG. 1,
FIG. 4 shows a sectional view of a pressing tool,
FIG. 5 shows a sectional view of the pressing tool in a first
state,
FIG. 6 shows a sectional view of the pressing tool in a second
state,
FIG. 7 shows a sectional view of the pressing tool in a third
state,
FIG. 8 shows a sectional view of the pressing tool in a fourth
state,
FIG. 9 shows a sectional view of the pressing tool in a fifth
state,
FIG. 10 shows a further embodiment of a sintered unit produced in
accordance with the proposed method,
FIG. 11 shows the unit from FIG. 10 in a sectional view,
FIG. 12 shows a further embodiment of a sintered unit produced in
accordance with the proposed method,
FIG. 13 shows the unit from FIG. 12 in a sectional view,
FIG. 14 shows a further refinement of a sintered unit produced in
accordance with the proposed method,
FIG. 15 shows a further refinement of a sintered unit produced in
accordance with the proposed method,
FIG. 16 shows a further refinement of a sintered unit produced in
accordance with the proposed method,
FIG. 17 shows a further refinement of a sintered unit produced in
accordance with the proposed method,
FIG. 18 shows a further refinement of a sintered unit produced in
accordance with the proposed method,
FIG. 19 shows a further refinement of a sintered unit produced in
accordance with the proposed method,
FIG. 20 shows a further refinement of a sintered unit produced in
accordance with the proposed method,
FIGS. 21 to 25 show a comparison, and photographs, of an
unpredictable crack characteristic in the case of conventional
technology, and
FIGS. 26 to 29 show further embodiments of a sintered unit equipped
with at least two predictable predetermined breaks.
FIG. 1 shows a sintered unit 1 having a first part 3 and a second
part 2 which are integrally connected to one another. The first
part 3 is in the form of a hexagon and is suitable for the
engagement of a wrench. In the usage situation illustrated in FIG.
1, the first part 3 of the sintered unit 1 is subjected to a torque
4. The torque 4 may preferably, in the installed state of the
sintered unit 1, be dissipated at a first side surface 5 and at a
second side surface 6, which is concealed in FIG. 1, wherein the
sintered unit 1 is braced by way of the side surfaces 5 and 6
against a further unit, for example against a wheel rim of a motor
vehicle.
FIG. 2 shows a first partial green product 11 and a second partial
green product 12. The second partial green product 12 is, in this
exemplary embodiment, of hexagonal shape. The hexagonal shape is
formed by way of six planar side surfaces such as the side surfaces
13 and 14, along with the side surfaces 15, 16, 17 and 18 that are
not visible in the illustration. The side surfaces 13, 14, 15, 16,
17 and 18 preferably have the same height and width. To form an
interference fit during the joining of the first partial green
product 11 to the second partial green product 12, the first
partial green product 11 has six side surfaces, such as the side
surfaces 23, 24, 25, 26, 27 and 28, wherein the side surfaces 23,
24, 25 and 28 are concealed in the perspective view illustrated in
FIG. 2.
Likewise, the side surfaces 23, 24, 25, 26, 27 and 28 have the same
height and width. To form an interference fit between the first
partial green product 11 and the second partial green product 12,
the side surfaces 23, 24, 25, 26, 27 and 28 have a length 29 which
corresponds approximately to a length 19 of the side surface 14,
wherein, in a preferred embodiment, the length 29 is smaller than
the length 19 by an oversize for generating an interference fit.
The oversize may lie in the range from approximately 0.005 to
approximately 0.05 mm.
FIG. 3 shows the sintered unit 1 with the first part 3 and the
second part 2 in a sectional view. The torque 4 acting on the first
part 3, as indicated in FIG. 1, is transmitted by way of at least
one contact surface 31 to the second part 2. According to the
invention, the sintered unit 1 has a predetermined breaking point
32 in a region 33, wherein the region 33 encompasses an
interference fit 34 which is formed between the first partial green
product 11 and the second partial green product 12 during the
joining of the first partial green product 11 to the second partial
green product 12. FIG. 3 duly illustrates the sintered unit 1, but
the dimensions of the sintered unit 1 substantially correspond to
the dimensions of a green product composite which has the first
partial green product 11 and the second partial green product 12,
aside from shrinkage of the partial green products 11 and 12
arising as a result of the sintering process. The distance 36 of
the predetermined breaking point 32 from the interference fit 34 of
the green product composite may amount to approximately one
thirtieth of the height 35 of the interference fit 34.
FIG. 4 shows a sectional view of a pressing tool 41 having a first
upper plunger 42 and a second upper plunger 43, a die 44, a first
lower plunger 45, a second lower plunger 46, a third lower plunger
47 and a mandrel 48. The mandrel 48 and the respective pressing
plungers are arranged relative to one another such that, in the
position of the pressing tool 41 shown in FIG. 4, they hold the
first partial green product 11 and the second partial green product
12 separate from one another.
FIG. 5 shows the pressing tool 41 in a first state, wherein the
first lower plunger 45, the second lower plunger 46, the third
lower plunger 47 and the mandrel 48 are arranged relative to one
another such that they form a common filling chamber 49 which is
delimited to the outside by the die 44. In a first step of the
proposed method, a powder 50 is introduced into said filling
chamber 49.
FIG. 6 shows the pressing tool 41 in a second state. In said second
state of the pressing tool 41, the pressing plungers 42, 43, 45, 46
and 47 and the mandrel 48 are arranged relative to one another such
that the common powder 50, which in the first state of the pressing
tool 41 has filled the entire filling chamber 49, is present in the
form of a first partial amount 51 and a second partial amount 52,
wherein the first partial amount 51 is separated from the second
partial amount 52.
FIG. 7 shows the pressing tool 41 in a third state, wherein the
first upper plunger 42, the second upper plunger 43, the first
lower plunger 45, the second lower plunger 46 and the third lower
plunger 47 are arranged relative to one another such that a pressed
first partial green product 11 is present between the first upper
plunger 42 and the first lower plunger 45 and the second lower
plunger 46 and the third lower plunger 47. In particular, the first
partial green product 11 is pressed by way of the first upper
plunger 42 and the first lower plunger 45 and the second lower
plunger 46, and is laterally delimited during the pressing by the
die 44 and by a sidewall 61 of the third lower plunger 47.
Furthermore, in the third state of the pressing tool, the second
upper plunger 43 and the third lower plunger 47 are arranged such
that the second partial green product 12 is present in pressed form
between said two pressing plungers. During the pressing, the second
partial green product 12 is delimited by an outer surface 62 of the
mandrel 48 and by an inner surface 63 of the first upper plunger
42.
FIG. 8 shows the pressing tool 41 in a fourth state, in which the
pressing plungers 42, 43, 45, 46, 47 and the mandrel 48 are
arranged relative to one another such that the first partial green
product 11 has been pressed together with the second partial green
product 12 to form a green product composite 71, wherein an
interference fit 72 is formed between the first partial green
product 11 and the second partial green product 12. In a particular
embodiment of the proposed method, the partial green product 11
and/or the partial green product 12 may also be pressed and/or
re-compacted during the joining.
FIG. 9 shows the pressing tool 41 in a fifth state, in which the
first upper plunger 42 and the second upper plunger 43 and the
lower plunger 45 have been moved upward and the mandrel 48 and the
lower plunger 47 have been moved downward, such that the green
product composite 71 is released. In said state of the pressing
tool, the green product composite 71 can be gripped, for example by
way of a gripping tool, and transported to a sintering furnace.
FIGS. 5 to 9 illustrate the individual steps of a pressing cycle
such as the introduction as per FIG. 5, the separation of the
powder 50 into a first partial amount 51 and a second partial
amount 52 as per FIG. 6, the compaction of the respective partial
amounts 51 and 52 to correspondingly form the first partial green
product 11 and the second partial green product 12 as per FIG. 7,
the joining of the first partial green product 11 to the second
partial green product 12 to form a green product composite 71, and
the release and/or discharge of the green product composite 71. A
pressing cycle comprises at least said five steps. According to the
invention, the pressing of the first partial green product 11 and
of the second partial green product 12 and the joining of the two
partial green products 11 and 12 to form the green product
composite 71 are performed within one pressing cycle within the
same pressing tool 41. Furthermore, it is provided according to the
invention that the interference fit 82 is formed during the joining
of the first partial green product 11 to the second partial green
product 12 and a predetermined breaking point 73 of the green
product composite 71 is formed in a region 74 in the vicinity of
the interference fit 72.
The method according to the invention furthermore provides that the
pressing process of the first partial green product 11 and of the
second partial green product 12 and the subsequent joining of the
two partial green products 11 and 12 is performed such that the
predetermined breaking point 73 of the green product composite 71
is situated in each case in the same region 74 of the produced
green product composites in a repeatable manner, preferably in a
series production context. This may be achieved in particular by
virtue of the partial amounts 51 and 52 being pressed to form
partial green products 11 and 12 with different density.
Preferably, the first partial green product 11 has a first density
and the second partial green product 12 has a second density,
wherein the second density may be lower than the first density.
The predetermined breaking point is preferably situated in a first
part of the green product composite in which the density is lower
than in a second part of the green product composite, in which the
density is relatively high. It is advantageously possible to set a
failure load, which is predefined for example by a predefined
equivalent stress, in particular a von Mises equivalent stress, by
way of a density difference between the first density and the
second density.
Here, the density difference may preferably amount to one SINT
class. In a further embodiment, the density difference may amount
to two SINT classes, and in a modified embodiment, said density
difference may amount to three SINT classes. For example, the first
partial green product 11 may be assigned to a SINT class D, and the
second partial green product 12 may be assigned to a SINT class C,
wherein, in this case, the density difference amounts to one SINT
class. In a second embodiment of the method, the two partial green
products 11 and 12 are compacted such that, after the compaction,
the first partial green product 11 can be assigned to the SINT
class D and the second partial green product 12 can be assigned to
the SINT class B, wherein, in this case, the density difference
amounts to two SINT classes. If the density difference has two SINT
class steps, it is thus possible, for example, to realize a
relatively low failure load of the fully sintered unit in relation
to a method in which the density difference between the first
partial green product 11 and the second partial green product 12
amounts to only one SINT class.
Through the setting of a targeted density difference, it is also
possible for the position of the predetermined breaking point to be
influenced. For example, in the case of a small density difference,
which amounts to for example only one SINT class, it is possible
for the predetermined breaking point to be positioned closer to the
interference fit 72 than in the case of a method in which the
density difference amounts to two SINT classes. In general, it is
then also possible for a density difference between the first
partial green product 11 and the second partial green product 12 to
be provided with a smaller graduation than one full SINT class, for
example one hundredth, one tenth, one fifth or one half of one SINT
class density range, wherein a SINT class density range is defined
by the lower density and the upper density of the corresponding
SINT class.
FIG. 10 shows a further embodiment of a sintered unit 81, which has
a first part 83 and a second part 82. The unit 81 is preferably
designed such that a torque 84 can be applied to the first part
83.
FIG. 11 shows the unit 81 in a sectional view, wherein a
predetermined breaking point 86 of the unit 81 is arranged in the
first part 83 in a region 85. In particular, the unit 81, in a
first embodiment, has the predetermined breaking point 86 in the
region 85, wherein the density difference between the first part 83
and the second part 82 amounts to approximately two SINT classes or
more. For example, the first part 83 of said embodiment may be
assigned to the SINT class B, and the second part 82 may be
assigned to the SINT class D. In a second embodiment that differs
therefrom, the unit 81 may have a predetermined breaking point 87
which is arranged in a region 88. In said embodiment, the density
difference between the first part 83 and the second part 82
preferably amounts to approximately one SINT class. For example,
the first part 83 may be assigned to the SINT class B and the
second part 82 may be assigned to the SINT class C.
FIG. 12 shows a further embodiment of a sintered unit 91 with a
first part 93 and a second part 92, wherein a torque 94 can be
applied in the interior of the first part 93.
FIG. 13 shows the unit 91 in a sectional view, wherein a
predetermined breaking point 96 of the unit 91 is arranged in the
first part 93 in a region 95. In particular, the unit 91, in a
first embodiment, has the predetermined breaking point 96 in the
region 95, wherein the density difference between the first part 93
and the second part 92 amounts to approximately two SINT classes or
more. For example, the first part 93 of said embodiment may be
assigned to the SINT class B, and the second part 92 may be
assigned to the SINT class D. In a second embodiment that differs
therefrom, the unit 91 may have a predetermined breaking point 97
which is arranged in a region 98. In said embodiment, the density
difference between the first part 93 and the second part 92
preferably amounts to approximately one SINT class. For example,
the first part 93 may be assigned to the SINT class B and the
second part 92 may be assigned to the SINT class C.
FIG. 14 shows a perspective view and a sectional view of a further
embodiment of a sintered unit 101 which is produced by way of the
method according to the invention and which has a first part 103
and a second part 102, wherein a torque 104 can be applied to the
outer edge of the second part 102. The predetermined breaking point
is situated in a region 105, preferably in the first part 103.
FIG. 15 shows a perspective view and a sectional view of a further
embodiment of a sintered unit 111 which is produced by way of the
method according to the invention and which has a first part 113
and a second part 112, wherein a tensile force 114 can be applied
to the outer edge of the first part 113. The predetermined breaking
point is situated in a region 115, preferably in the first part
113.
FIG. 16 shows a perspective view and a sectional view of a further
embodiment of a sintered unit 121 which is produced by way of the
method according to the invention and which has a first part 123
and a second part 122, wherein a tensile force 124 can be applied
to the outer edge of the first part 123. The predetermined breaking
point is situated in a region 125, preferably in the first part
123. In this embodiment, the action of the predetermined breaking
point can be intensified by way of a notch effect at the transition
from the first part 123 to the second part 122.
FIG. 17 shows a perspective view and a sectional view of a further
embodiment of a sintered unit 131 which is produced by way of the
method according to the invention and which has a first part 133
and a second part 132, wherein a shear force can be applied to a
sidewall of the first part 133. The predetermined breaking point is
situated in a region 135, preferably in the first part 133. In this
embodiment, the predetermined breaking point fails by way of a
shear crack.
FIG. 18 shows a perspective view and a sectional view of a further
embodiment of a sintered unit 141 which is produced by way of the
method according to the invention and which has a first part 143
and a second part 142, wherein a lateral force 144 can be applied
to the first part 143, which is of elongate form in relation to the
second part 142. The predetermined breaking point is situated in a
region 145, preferably in the first part 143. In this embodiment,
the predetermined breaking point fails as a result of a bending
stress exceeding a failure load of the unit 141.
FIG. 19 shows a perspective view and a sectional view of a further
embodiment of a sintered unit 151 which is produced by way of the
method according to the invention and which has a first part 153
and a second part 152, wherein a torque 154 can be applied to the
outer edge of the second part 152. The predetermined breaking point
is situated in a region 155, preferably in the first part 153. In
this embodiment, the action of the predetermined breaking point can
be intensified by way of a notch effect owing to the encircling
notch 156.
FIG. 20 shows a perspective view and a sectional view of a further
embodiment of a sintered unit 161 which is produced by way of the
method according to the invention and which has a first part 163
and a second part 162, wherein a torque 164 can be applied to the
outer edge of the second part 162. The predetermined breaking point
is situated in a region 165, preferably in the first part 163. In
this embodiment, the action of the predetermined breaking point can
be intensified by way of a notch effect, preferably by way of an
engagement of a torque support 166.
In the exemplary embodiments in FIGS. 14 to 20, the parts 103, 113,
123, 133, 143, 153 and 163 in each case have lower densities than
the parts 102, 112, 122, 132, 142, 152 and 162, wherein the
position of the respective predetermined breaking point is realized
in the parts with the relatively low density, that is to say the
parts 103, 113, 123, 133, 143, 153 and 163. In the case of units
which are produced by sintering of a green product composite having
more than two partial green products, it is also possible for
multiple predetermined breaking points to be formed, which fail
under the action of different loads.
FIG. 21 shows a comparison of an identical unit A, B, as has
already been described above, produced and sintered in each case
from powder material, which unit has in one case been produced in
accordance with the green-in-green method described above (unit A)
for creating the in each case homogeneously pressed partial green
products, and has in another case been produced by way of
conventional technology (unit B). Whereas, in the case of unit A,
in each case two homogeneous bodies 201, 202 are in each case
homogeneous in themselves, which makes it possible for example to
utilize different densities, unit B has no partial bodies, but
rather has a single integrated body 203, which in the transitions
204 has in each case critical regions characterized by
inhomogeneities and microcracks. The latter do not permit reliable
predictability with regard to a fracture of the unit B. The problem
of uncontrollable microcracks and inhomogeneities is illustrated on
the basis of the following FIGS. 22 to 25, which show various
cracks produced in a unit B by way of conventional technology.
FIG. 22 shows a brittle crack at a transition of the unit B at the
top left, as occurs as a result of the release of load in the press
in the case of conventional green product production, and which
leads either directly, or only at a later point in time, to a
complete, uncontrollable and unpredictable failure of the unit.
Such a brittle crack may exist undiscovered within the unit, but
later leads to failure during use as a result of crack growth, even
though the actually calculated torque action for this has not yet
been applied.
FIG. 23 shows a grinding pattern through a green product of a unit
B, in the case of which firstly an uncontrollable dead-water crack
and secondly also a shear crack have been identified in the case of
the conventional production technology being used.
FIG. 24 shows a further grinding pattern through a green product of
the unit B. Here, a shear crack has been found within the
microstructure, said shear crack being caused by inhomogeneities
owing to deformed particles.
FIG. 25 shows a further grinding pattern through a green product of
the unit B with a dead-water crack. The dead-water crack extends
laterally from the transition, extends to a depth and subsequently
upward into the relatively narrow region. In this way, a breakaway
from the transition occurs.
FIG. 26 shows, in an exemplary embodiment, a unit which is produced
in accordance with the "green-in-green" method according to the
invention and which is configured with a respectively predefinable
predetermined break and which has a main body 205 from which two
components 206, 207 project, which components fail under the action
of mutually different forces F1, F2, for example, as illustrated,
owing to shear. Here, different cross sections and/or different
densities may be used in order to realize different strengths.
Aside from a pressure load, it is also possible for a torque load,
a bending load and/or a tensile load to be utilized to achieve a
respective predetermined break under predefinable conditions in the
case of a safety unit. Aside from two, it is also possible for more
components to be provided, which, configured in each case
differently from one another, undergo a predetermined break. The
main body 205 preferably has a geometry such that its
circumferential surface 208 can be utilized as a means for
dissipating a force and/or a moment and/or for transmitting an
opposing pressure or an opposing moment.
FIG. 27 shows, in a schematically simplified illustration, the
region 209 in which, in each case, the predetermined break reliably
occurs. By way of the homogeneous compaction of the respective
partial green products joined one inside the other by way of an
interference fit, reliable predictability of failure, and thus
usage as a safety component with a predetermined break for safety
purposes, are possible.
FIG. 28 shows a further unit with mutually concentrically arranged
components in a main body 212. In the example illustrated, it is
sought to realize a safety action when shearing and bending occur.
The components 210, 211 fail under the action of different forces
F1, F2. In this example, it is also possible for a force F1 to
impart a bending load and for a force F2 to impart a shear load.
Here, use may likewise be made of different cross sections and/or
different densities in order to realize different strengths. A
torque load and/or tensile load is also conceivable, as are
combinations of the various forces and moments.
FIG. 29 shows, in a schematic view relating to FIG. 28, the regions
in which the predetermined break predictably takes place. Whereas,
in an upper region of the failure 213, said failure occurs for
example owing to notch stresses, it is the case in a lower region
of the failure 214 that said failure occurs for example by way of a
shear crack.
The configuration of the unit makes it possible, for example
utilizing a notch effect of a geometric form, to permit a reliable
predetermined break even in the case of sintered units produced
from metallic or ceramic powder. In this way, a sintered body of
said type can be used as a safety unit.
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